/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.tags;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.servlet.support.JspAwareRequestContext;
import org.springframework.web.servlet.support.RequestContext;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.TagSupport;
import javax.servlet.jsp.tagext.TryCatchFinally;

/**
 * Superclass for all tags that require a {@link RequestContext}.
 *
 * <p>The {@code RequestContext} instance provides easy access
 * to current state like the
 * {@link org.springframework.web.context.WebApplicationContext},
 * the {@link java.util.Locale}, the
 * {@link org.springframework.ui.context.Theme}, etc.
 *
 * <p>Mainly intended for
 * {@link org.springframework.web.servlet.DispatcherServlet} requests;
 * will use fallbacks when used outside {@code DispatcherServlet}.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see org.springframework.web.servlet.support.RequestContext
 * @see org.springframework.web.servlet.DispatcherServlet
 */
@SuppressWarnings("serial")
public abstract class RequestContextAwareTag extends TagSupport implements TryCatchFinally {

    /**
     * {@link javax.servlet.jsp.PageContext} attribute for the
     * page-level {@link RequestContext} instance.
     */
    public static final String REQUEST_CONTEXT_PAGE_ATTRIBUTE =
            "org.springframework.web.servlet.tags.REQUEST_CONTEXT";


    /**
     * Logger available to subclasses.
     */
    protected final Log logger = LogFactory.getLog(getClass());


    @Nullable
    private RequestContext requestContext;


    /**
     * Create and expose the current RequestContext.
     * Delegates to {@link #doStartTagInternal()} for actual work.
     *
     * @see #REQUEST_CONTEXT_PAGE_ATTRIBUTE
     * @see org.springframework.web.servlet.support.JspAwareRequestContext
     */
    @Override
    public final int doStartTag() throws JspException {
        try {
            this.requestContext = (RequestContext) this.pageContext.getAttribute(REQUEST_CONTEXT_PAGE_ATTRIBUTE);
            if (this.requestContext == null) {
                this.requestContext = new JspAwareRequestContext(this.pageContext);
                this.pageContext.setAttribute(REQUEST_CONTEXT_PAGE_ATTRIBUTE, this.requestContext);
            }
            return doStartTagInternal();
        } catch (JspException | RuntimeException ex) {
            logger.error(ex.getMessage(), ex);
            throw ex;
        } catch (Exception ex) {
            logger.error(ex.getMessage(), ex);
            throw new JspTagException(ex.getMessage());
        }
    }

    /**
     * Return the current RequestContext.
     */
    protected final RequestContext getRequestContext() {
        Assert.state(this.requestContext != null, "No current RequestContext");
        return this.requestContext;
    }

    /**
     * Called by doStartTag to perform the actual work.
     *
     * @return same as TagSupport.doStartTag
     * @throws Exception any exception, any checked one other than
     *                   a JspException gets wrapped in a JspException by doStartTag
     * @see javax.servlet.jsp.tagext.TagSupport#doStartTag
     */
    protected abstract int doStartTagInternal() throws Exception;


    @Override
    public void doCatch(Throwable throwable) throws Throwable {
        throw throwable;
    }

    @Override
    public void doFinally() {
        this.requestContext = null;
    }

}
